Merge remote-tracking branch 'remotes/agraf/tags/signed-ppc-for-upstream' into staging

Patch queue for 2.3 ppc - 2015-03-25

Just a few bug fixes before 2.3 gets released:

  - pseries: Firmware update, bugfixes
  - remove POWER5+ v0.0 that we incorrectly introduced in 2.3
  - Fix -machine usb=no
  - Fix -boot once=foo in pseries
  - Add NULL pointer check in pseries machine init

# gpg: Signature made Wed Mar 25 21:53:20 2015 GMT using RSA key ID 03FEDC60
# gpg: Good signature from "Alexander Graf <agraf@suse.de>"
# gpg:                 aka "Alexander Graf <alex@csgraf.de>"

* remotes/agraf/tags/signed-ppc-for-upstream:
  powerpc: fix -machine usb=no for newworld and pseries machines
  PPC: pseries: Implement boot once=foo
  target-ppc: Remove POWER5+ v0.0 that never existed
  spapr: Add missing checks for NULL pointers and report failures
  pseries: Update SLOF firmware image to qemu-slof-20150313

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>